Many objects have intrinsic value or have value because they provide access to other valuable objects. For instance, jewelry and coins have inherent intrinsic value while keys, such as keys to vehicles, have value because they provide access to other valuable objects, namely automobiles and trucks. Further, access to and control of some items, such as narcotics for example, needs to be monitored, tracked, and controlled to assure against unauthorized access or assure that proper and appropriate accesses is catalogued. There is a serious need to be able to track, catalogue access to, and control such objects in a way that is reliable, simple to implement, and virtually tamper proof.
In the past, a variety of systems have been implemented to track and control objects. In the case of keys in an automobile dealership, for example, pegboards have been used to keep track of the keys as sales persons, maintenance personnel, and others remove keys for access to vehicles. Generally, sign out sheets are used to log the check-in and checkout of such keys. Obviously, such a manual system of tracking has numerous shortcomings due in large part to the very real potential of human error and forgetfulness in carrying out the sign-in and sign-out procedures.
More recently, automated computer controlled key tracking systems have been implemented for tracking, for example, vehicle keys at car lots and keys to the apartments of apartment complexes. One such system particularly applicable to the present invention is the key tracking system disclosed and claimed in my U.S. Pat. No. 5,801,628, the disclosure of which is hereby incorporated fully by reference. In the disclosed system, referred to herein as the "Key Track" system, keys to a vehicle are attached with a rivet, tether, or the like to a thin plastic key tag or card having a depending tongue. The tongue carries a small button shaped electronic touch memory device, which electronically stores an ID code. The tongue of each key card is configured to be insertable in any of an array of slots formed in a top panel within a storage drawer. A printed circuit backplane is disposed beneath the top panel and is provided with a plurality of pairs of metal contacts, each pair of contacts being aligned with a corresponding one of the slots in the top panel. When the tongue of a key card is inserted in a selected one of the slots, its touch memory device is engaged by the corresponding pair of contacts.
A computer or microprocessor or microcontroller based controller is electronically coupled through a communications matrix to the contacts on the backplane and periodically polls each pair of contacts, preferably several times per second, to determine the presence or absence of a touch memory device and thus which slots contain key cards and which do not. More specifically, if no information is received from a particular pair of contacts when polled, it is determined that the slot corresponding to the pair of contacts is empty. When a slot contains a key card, the touch memory device of the card responds to the poll by transmitting its ID code, from which the identity of the particular key attached to the card can be determined through a table lookup. In this way, the absence or presence and location in the storage drawer of key cards and their associated keys can be noted by the controller each time the array of contacts are polled. If a card present in a slot on a prior polling is absent on a subsequent polling, then the controller notes that the card and its key have been removed from the storage drawer. Conversely, if a key card is detected in a previously empty slot, the controller notes that the card and its key have been replaced in the storage drawer. The removal and replacement of keys is therefore continuously monitored.
An access feature requires an authorized user such as a sales person to enter an ID code to unlock and access the storage drawer. When the history of removal and replacement of key cards and their keys is combined with other information, such as the time at which cards are removed and replaced and the identities of the persons who accessed the drawer and times of access, access to the keys in the drawer can be controlled and a detailed tracking log can be created. This Key Track system greatly decreases instances of lost keys, reduces the time required to find checked-out keys, and generally provides automatic tracking and control of the keys, and thus, to a large extent, controls and tracks the vehicles to which the keys provide access.
As an alternative to a Key Track system using touch memory devices requiring physical engagement with conducting contacts, non-contact transmission of ID codes to the controller are also possible. Such systems make use of radio frequency (RF) tags on the key cards with the tags having an integrated circuit chip storing the ID code and perhaps other information and an antenna attached to the chip. The antenna can be a capacitive plate antenna, an inductive loop antenna, a dipole antenna, or another type of antenna. The backplane of the system includes an array of sensors in the form of antennas that are positioned to align with the antennae on the key cards when the cards are inserted within their slots or receptacles in the storage unit. Information is transmitted from the cards to the controller via radio frequency transmission or modulation from the antennas on the key cards to the sensor antennas on the backplane. Aside from the non-contact method of data transmission, the functionality of such systems is much the same as a system using touch memory devices.
While the Key Track system described above has proven extremely valuable in the tracking and control of keys, it nevertheless has certain problems and shortcomings inherent in its design. One such problem is the potential for tampering and system defeat simply by cutting the key card or cutting the key in order to remove the key from the card without removing the card from the Key Track storage drawer. In such an event, the key card remains in its slot so the Key Track controller fails to note any suspicious activity, thinking instead that the key is still secure within the storage drawer. Even though a subsequent user of the system my notice that the key has been removed from its card, this may not occur for some time and, by then, the key (or other valuable object that may have been attached to the card) may well be beyond recovery. Further, relying on humans to report system compromises allows for the potential for conspiracy, and is thus generally not reliable.
Thus, a need exists for a method and system for detecting tampering and attempted defeat of a Key Track system by removing a key or other valuable item from its Key Track card while leaving the card intact within the Key Track storage drawer. In a broader sense, the system should be adaptable for use with Key Track systems utilizing touch memory devices and non-contact RF tag devices for storing and transmitting ID codes to the system controller. The system should be reliable, should indicate tampering with a high level of confidence when it occurs, and should operate autonomously without the need for relying on human intervention for detecting and reporting tampering. It is to the provision of such a method and system that the present invention is primarily directed.